AZ_FTBR_DAVIS_DAM_ROAD_(1)_Davis_Dam_Road_Rehabilitation_Pavements_Memorandum_-_FINAL.pdf

Memorandum

Subject: AZ FTBR DAVIS DAM ROAD (1) Davis Dam Road Rehabilitation Pavement Recommendations

Date: November 20, 2017

From: Mike Voth Pavements and Materials Team Leader, CFLHD

To: Brent Nagen, PM/COE Jeff Felling, Lead Designer

Background:

This memorandum provides the pavement structural section recommendation for the AZ FTBR DAVIS DAM ROAD (1), Davis Dam Road Rehabilitation project The total length of the proposed project at the time of this memorandum is 0.35 miles. The proposed project is located on Davis Dam Road, beginning at the bridge over the Davis Dam spillway, and terminating at the realigned intersection with Katherine Drive. The Route is considered a rural, recreational and scenic road, with primary traffic composed of Bureau of Reclamation (BOR) employees. The proposed project includes full depth reclamation with an asphalt concrete pavement overlay.

No formal traffic data is believed to exist. Anecdotal data provided by the BOR indicates the route is low volume, with less than 100 ADT. The adjacent intersection realigned under the NV FTNP LAKE 114(1) project utilized a new structural section of 3” HMA placed on 8” roadway aggregate. The traffic for Katherine Drive/Davis Dam Road to this intersection is considerably higher than the segment of Davis Dam Road proposed.

Given the proposed scope/length of the project and relevant information from an adjacent project, a pavements investigation was not proposed for the project. While the existing pavement structural section was not investigated to determine layer types and thickness, it is evident from photos (see attachment) that there is a layer of hot mix asphalt over either granular subgrade or an old aggregate base. The closest R-Value from the LAKE 114(1) report, taken at the intersection and near the end of this project, indicates a value of 74.

Recommendations:

Currently, the project length totals 1,833 feet with approximately 1,000 tons of hot mix.

Based on the project length, scope and the above and referenced information, the following is recommended:

3 inches HACP (Section 403) 6 inches Full Depth Reclamation (Section 304)

The road is highly distressed and not a candidate for a simple overlay. Full depth reclamation (FDR) will pulverize the existing asphalt pavement and blend it with a portion of the base below to create an excellent foundation for paving. The re-use and recycling of the existing materials is cost efficient and will provide for good long-term pavement performance.

Using 75,000 ESALs for traffic and a conservative resilient modulus of 10,000 psi, the above recommended pavement section will provide for a 20-year service life. The design SN required is 1.82 and the above pavement section provides a SN of 1.92.

It is recommended that the asphalt pavement be placed in two lifts and a tack coat included between the pavement lifts. It is also recommended that a prime coat be applied to the FDR layer. Unless otherwise indicated by the project engineer, the final surface will receive a fog seal. Include quantities for fog seal and blotter in the contract.

Areas with aprons or pull-outs should have 6 inches of aggregate base followed by a 3-inch asphalt overlay.

Recommended Pay Items for this Project:

Item Number Item Description Unit 30202-2000 Roadway Aggregate, Method 2 TON 30402-5300 Full Depth Reclamation, Method 2, 6-Inch Depth SQYD 40301-0100 Asphalt Concrete Pavement, Type 1 TON 40601-0000 Fog Seal TON 41102-1000 Prime Coat, Method 1 SQYD 41201-0000 Tack Coat TON

A discretionary quantity of subexcavation, 100 CY, should also be included in the bid schedule.

Any applicable Special Contract Requirements will follow at a later time and under separate cover. The pay items above are to be constructed using the FP-14.

Attachment:

Scoping Photos

11/03/2017

Scoping Trip Photos June 1, 2017

Typical condition: raveling surface, high severity block cracking

Typical condition: approaching dam

Typical condition: narrow area, through cut

Typical condition: raveling surface, delamination

Existing pavement thickness and base / subgrade. Will accommodate FDR operations.